This invention relates to a system for treating material, for example, in the course of drying, heating, cooling, reacting and recrystallizing material. In particular, the invention comprises a method and apparatus for handling flowable material whereby the material can be treated in some fashion in the course of its progression through the apparatus.
The invention comprises an apparatus and method which may be implemented utilizing components of an apparatus of the type generally described in U.S. Pat. No. 3,425,135. This apparatus consists of an elongated vessel of substantially circular cross section having an axially mounted rotatable shaft disposed therein. A plurality of paddles or vanes are mounted on the rotatable shaft, and these extend substantially to the inside wall of the vessel. Typically, the vessel is disposed either horizontally or having a modest upward or downward inclination with respect to the horizontal from the material inlet end of the apparatus to the outlet thereof.
As described in the aforementioned patent, the cylindrical housing comprising the vessel is desirably jacketed to permit the circulation of heating or cooling medium adjacent the inside wall of the vessel. By introducing flowable material at one end of the vessel, treatment of the material is achieved through heat exchange between the material and the inside wall. The flowable material may comprise, for example, wet or dry solids, slurries, gels or wet cakes from filters and centrifuges.
As further described in the aforementioned patent, the paddles utilized in the system tend to propel the material in a spiral or helical path between the material inlet and outlet. As illustrated in the patent, the paddles generate a thin dense layer of material in a form of a ribbon-type flat spiral moving around the inner surface of the housing. In this way, only part of the heat transfer surface area available is covered by the material being treated. The centrifugal action of the rotating agitator decreases the mixing between particles in the dense layer of material thus reducing the heat and mass transfer rate.